(b)
(c)
(d)
(e)
16.6
(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
Figure 16.12: AM1.5 spectrum and its simplified representation in blue.
Not all energy of an absorbed photon (E) is used to excite the electron from the valence to the
conduction band (E g ). E − E g is lost as heat. Consider an ideal solar cell, i.e. EQE = 1 for all energies
above the bandgap. For simplicity, we neglect possible reflection of light from the window layer(s).
Show that the irradiance lost as heat can be described by:
Consider a single-junction solar cell based on a semiconductor material with a band gap of 0.67 eV.
Again, consider EQE = 1 for energies above the bandgap. How much of the irradiance is lost as heat
(expressed in W/m 2 )?
The single-junction solar cell in the above question is now integrated as bottom cell in a double-junction
solar cell. The bandgap of the absorber material of the top cell is 1.24 eV. Again, consider EQE = 1 for
energies above the bandgap. How much of the irradiance is lost as heat (expressed in W/m 2 ) in this
double junction solar cell?
A triple junction has been processed using various III-V alloys. The EQE of the individual cells can be
considered as a block function with EQE = 0.8. The bandgap of the bottom cell is 0.67 eV. The short
circuit current density of the triple junction is J sc = 15 mA.cm −2 . What are the smallest values for both
bandgaps expressed in eV of the middle and top cells?
The spectral irradiance of the AM1.5 solar spectrum is shown in Figure 16.13 (a). A rough approximation of
the AM1.5 spectrum is represented by the blue region, which will be used as the input solar spectrum in this
particular exercise. The spectral irradiance of the simplified spectrum is given by:
I eλ = 0.50 × 10 9 Wm −2 m −1 for 250 nm < λ < 2, 250 nm.
The band diagram of an intermediate band solar cell is depicted in Figure 16.13 (b). The bandgap is 1.5 eV, the
intermediate band is 1.0 eV above the valence band and 0.5 eV below the conduction band. Assume that every
photon above the bandgap is absorbed and creates charge carriers, i.e. EQE = 100 %. All photons between 1.0
eV and 1.5 eV excite an electron from the valence to the intermediate band, whereas all photons between 0.5
eV and 1.0 eV excite an electron from the intermediate band to the conduction band. Reflection losses can be
neglected. For questions (a) to (c), ignore the intermediate band depicted in Figure 16.13 (b).
Plot the photon utilization efficiency (PUE) of the solar cell.
What amount of irradiance expressed in Wm −2 is used to excite an electron from the valence to the
conduction band under the condition as described in (a)?
How much photon flux is absorbed and what is the short circuit current density, J sc ?
For questions (d) to (h), also consider the intermediate band depicted in Figure 16.13 (b).
What is the photon flux absorbed in the spectral range of 1.0 eV up to 1.5 eV?
What is the photon flux absorbed in the spectral range of 0.5 eV up to 1.0 eV?
Plot the PUE of the intermediate band solar cell.
What is the total short circuit current density, J sc of the intermediate band solar cell?
What amount of irradiance expressed in Wm −2 is used to excite an electron from the valence to the
conduction band in the intermediate band solar cell?
(c)
(d)
(e)
16.6
(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
Figure 16.12: AM1.5 spectrum and its simplified representation in blue.
Not all energy of an absorbed photon (E) is used to excite the electron from the valence to the
conduction band (E g ). E − E g is lost as heat. Consider an ideal solar cell, i.e. EQE = 1 for all energies
above the bandgap. For simplicity, we neglect possible reflection of light from the window layer(s).
Show that the irradiance lost as heat can be described by:
Consider a single-junction solar cell based on a semiconductor material with a band gap of 0.67 eV.
Again, consider EQE = 1 for energies above the bandgap. How much of the irradiance is lost as heat
(expressed in W/m 2 )?
The single-junction solar cell in the above question is now integrated as bottom cell in a double-junction
solar cell. The bandgap of the absorber material of the top cell is 1.24 eV. Again, consider EQE = 1 for
energies above the bandgap. How much of the irradiance is lost as heat (expressed in W/m 2 ) in this
double junction solar cell?
A triple junction has been processed using various III-V alloys. The EQE of the individual cells can be
considered as a block function with EQE = 0.8. The bandgap of the bottom cell is 0.67 eV. The short
circuit current density of the triple junction is J sc = 15 mA.cm −2 . What are the smallest values for both
bandgaps expressed in eV of the middle and top cells?
The spectral irradiance of the AM1.5 solar spectrum is shown in Figure 16.13 (a). A rough approximation of
the AM1.5 spectrum is represented by the blue region, which will be used as the input solar spectrum in this
particular exercise. The spectral irradiance of the simplified spectrum is given by:
I eλ = 0.50 × 10 9 Wm −2 m −1 for 250 nm < λ < 2, 250 nm.
The band diagram of an intermediate band solar cell is depicted in Figure 16.13 (b). The bandgap is 1.5 eV, the
intermediate band is 1.0 eV above the valence band and 0.5 eV below the conduction band. Assume that every
photon above the bandgap is absorbed and creates charge carriers, i.e. EQE = 100 %. All photons between 1.0
eV and 1.5 eV excite an electron from the valence to the intermediate band, whereas all photons between 0.5
eV and 1.0 eV excite an electron from the intermediate band to the conduction band. Reflection losses can be
neglected. For questions (a) to (c), ignore the intermediate band depicted in Figure 16.13 (b).
Plot the photon utilization efficiency (PUE) of the solar cell.
What amount of irradiance expressed in Wm −2 is used to excite an electron from the valence to the
conduction band under the condition as described in (a)?
How much photon flux is absorbed and what is the short circuit current density, J sc ?
For questions (d) to (h), also consider the intermediate band depicted in Figure 16.13 (b).
What is the photon flux absorbed in the spectral range of 1.0 eV up to 1.5 eV?
What is the photon flux absorbed in the spectral range of 0.5 eV up to 1.0 eV?
Plot the PUE of the intermediate band solar cell.
What is the total short circuit current density, J sc of the intermediate band solar cell?
What amount of irradiance expressed in Wm −2 is used to excite an electron from the valence to the
conduction band in the intermediate band solar cell?